Morgoth is almost an exception to these rules ( 'oft evil will mar' / 'eveil overlord syndrome'). He is twice assaulted by the Valar because his acts become so intolerable but even though he is defeated both times he always has contingency plans in place - Utumno is destroyed but Angband is his fall-back. Angband is later assaulted in the War of Wrath but there are deeper pits dug to hide in just in case, and Ancalagon the Black is held back in reserve. Morgoth loses but he always seems to calculate more variables than Sauron.

And some other examples:

Morgoth overreaches when he becomes too incarnate within Arda and is thus vulnerable to 'death'? Yes but by the same token his essence is so disseminated that the whole of Arda is Marred.

Morgoth and Ungoliant fall out over the spoils of Valinor? Well yes but Morgoth triumphs because he has a few Balrogs he can call on. In fact, Ungoliant aside, there's little dissent in Beleriand when it comes to the forces of Evil. Morgoth runs a pretty tight ship. It's the Free Peoples who are disorganised and who fight amongst themselves.

A counter-example is the ridiculous amount of effort Morgoth seems to invest in bringing down Húrin's family. This fatal curse certainly leads to the tragic, bitter deaths of Húrin and his family but it also indirectly leads to the destruction of Morgoth's greatest (pre-Ancalagon) creation, Glaurung. What's more, Túrin remains so homicidal even in the afterlife that, according to the Second Prophecy of Mandos, he returns to kill Morgoth once and for all in the Dagor Dagorath.

Any other examples out there, either way? Welcome to the Mordorfone network, where we put the 'hai' back into Uruk